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Chemistry and petrography of calcite in the KTB pilot borehole, Bavarian Oberpfalz, Germany

Chemical Geology

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DOI: 10.1016/0009-2541(95)00063-R

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Abstract

The KTB pilot borehole in northeast Bavaria, Germany, penetrates 4000 m of gneiss, amphibolite, and subordinate calc-silicate, lamprophyre and metagabbro. There are three types of calcite in the drilled section: 1) metamorphic calcite in calc-silicate and marble; 2) crack-filling calcite in all lithologies; and 3) replacement calcite in altered minerals. Crack-filling and replacement calcite postdate metamorphic calcite. Multiple calcite generations in individual cracks suggest that different generations of water repeatedly flowed through the same cracks. Crack-filling mineral assemblages that include calcite originally formed at temperatures of 150-350??C. Presently, crack-filling calcite is in chemical and isotopic equilibrium with saline to brackish water in the borehole at temperatures of ???120??C. The saline to brackish water contains a significant proportion of meteoric water. Re-equilibration of crack-filling calcite to lower temperatures means that calcite chemistry tells us little about water-rock interactions in the crystal section of temperatures higher than ~120??C. -from Author

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Chemistry and petrography of calcite in the KTB pilot borehole, Bavarian Oberpfalz, Germany
Series title:
Chemical Geology
DOI:
10.1016/0009-2541(95)00063-R
Volume
124
Issue:
3-4
Year Published:
1995
Language:
English
Publisher:
Elsevier
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Chemical Geology
First page:
199
Last page:
215